A fuel cell utilizing hydrogen and oxygen attracts increasing attention as clean energy generation means that impose little environmental load since its only reaction product is only water in principle. A polymer electrolyte fuel cell, among others, is easy to handle and is promising in terms of output power density so that research and attempts for its practical application has become more and more active. Field of its application is very wide, including, for example, a power source for moving body such as an automobile or a bus, a stationary power source for a common home, a power supply for a small mobile terminal, and the like.
A polymer electrolyte fuel cell is composed by laminating a multiplicity of single cells each having typical structure as shown in FIG. 1, in which a polymer electrolyte membrane (ion exchange membrane) 10 is sandwiched between a pair of catalyst electrode layers 20, 21 from both sides, and these catalyst electrode layers 20, 21 are sandwiched between a pair of gas diffusion layers (also referred to as porous support layers or carbon fiber current collector layer) 40, 41. The gas diffusion layers 40, 41 are opened on the outside to gas passages (fuel gas passage 50, oxygen containing gas passage 51) formed by separators 60, 61. Fuel (such as H2) gas introduced from the passage 50 flows through a first gas diffusion layer (anode-side gas diffusion layer) 40, and then in a first catalyst electrode layer (anode, fuel electrode) 20, generates protons (H+) while emitting electrons in an anode reaction shown below. The protons flow through the polymer electrolyte layer 10, and then in a second catalyst electrode layer (cathode, oxygen electrode) 20, generates H2O and accepts electrons in a cathode reaction shown below.
anode reaction: H2→2H++2e−
cathode reaction: 1/2O2+2H+→H2O
As a conventional method for laminating and bonding a solid polyelectrolyte film to an electrode sheet (a catalyst layer formed on a gas diffusion layer), a bonding method has been disclosed in which a metallic mesh and a polytetrafluoroethylene sheet are additionally laminated and hot-pressing is carried out for bonding (see Patent Literature 1). It is disclosed that, with this method, the problems of damage of electrode sheets and softening of electrode sheets resulting in sticking to the press plate during hot-pressing carried out on the laminate formed of the solid polyelectrolyte film and the electrode sheets can be overcome.